The head of South Korea's national police has visited the Takeshima Islands. Japan's foreign minister said the country cannot tolerate the visit.
South Korea controls the islands. Japan claims them. The Japanese government maintains the islands are an inherent part of Japan's territory. It says South Korea is illegally occupying them.
The Korean National Police Agency said Commissioner General Kim Chang-yong landed on the islands in Shimane Prefecture, Japan, on Tuesday. South Korea calls the islands Dokdo.
Yonhap news agency reported that the visit took place after all security personnel on the islands were replaced by police officers this year. The agency said Kim encouraged them and inspected the islands.
The agency said the last visit by a police chief was in 2009.
Japan's Foreign Minister Hayashi Yoshimasa said Japan cannot tolerate the visit, if it took place. He said the islands are clearly an inherent part of Japan's territory in light of historical facts and based on international law. Hayashi said Japan will respond firmly to protect its land, territorial waters and airspace.
The government lodged a strong protest against South Korea.